Two cochleas with permanent, noise-induced threshold shifts of 40 to 60 dB (as measured
by responses of single, auditory-nerve fibers) were analyzed in detail, first at the light-
microscopic level and subsequently with transmission electron microscopy of serial sections.
The light-microscopic analysis showed that there was little hair cell loss, but widespread
damage to the stereocilia, especially those on the inner hair cells and first-row outer hair
cells. Transmission electron microscopy revealed no pathology in any cells or organelles in …